Re: Variac Troubles -Oops!

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Terry Fritz" <twftesla-at-qwest-dot-net>

Hi Winston,

At 03:46 PM 9/29/2002 -0700, you wrote:
>Hi Guys,
>
>	Responding to my own post here.  A word of advice to all:  Don't
>inspect new equipment while tired ;-)).  I tackled the thing again, with
>the benefit of some sleep, and found that it IS a 120VAC unit, probably
>rated for 70 amps.  I believe it to be a "standard" Powerstat 1156. 
>There are two windings in parallel, wound on the same core type as the
>1256, although they disguise this very well ;-)).  Those wires are hard
>to trace, even though there aren't very many of them.

Glad it's solved ;-)  Been there, done that :o))

>
>	More questions...  I didn't clean the area where the brushes slide
>across the windings, so the brushes spark when controlling even a lowly
>12/60 NST.  Will a simple contact cleaning fix this?  This variac was
>left outside for a LONG time, and had dirt in the windings and all the
>bearings/contacts.  The oxide coat on winding is pretty thick.  What
>have you guys found to reduce brush sparking???  I want to put a few
>taps on this thing, but don't quite know what I'm getting into here. 
>Suggestions???

Fine grade (200-400) wet dry sand paper with a little water or alcohol will
bring the sufaces back fine.  I think they are originally plated with brass
so go real easy on them.  Also, check the brush real close to be sure the
spring and brush move freely with the proper pressure.  If it is very dirty
you may want to take it all apart and wash it up and relube everything so
it is like new.  There are also fancy fiberglass contact cleaners that work
well too but read the instructions and cautions.

You can usually slide a piece of card under one of the windings, scrape the
enamal off, and solder on a new tape point with little problem if you want to. 

>
>Now feeling quite stupid,

Any of us who have worked with variacs have spent some time trying to trace
out the wires and all that.  No worries ;-))

Cheers,

	Terry


>Winston K.
>
>Tesla list wrote:
>> 
>> Original poster: "Marry Krutsch by way of Terry Fritz 
><twftesla-at-qwest-dot-net>" <u236-at-earthlink-dot-net>
>> 
>> Hi All,
>> 
>>         I just bought what APPEARED to be a 1256 Powerstat variac.  The 
>trouble
>> is, it saturates beyond 120 VAC in.  The new unit is identical to my
>> existing 1256, except for the wiring beneath the binding posts.  The new
>> unit looks like it uses the whole winding, but there are wires that go
>> someplace INSIDE the core.  I can't tell where these wires go.
>> 
>>         Is it possible that this variac uses a different core material,
which
>> saturates more easily?  I say again that the two units are IDENTICAL in
>> every way other than that stated above.
>> 
>> Please help, I'm stumped :-P.
>> Winston K.
>